See discussion on commit c9b022b5

If we overwrite the Server header, it becomes difficult/impossible to
know from the client whether the request was proxied through Caddy.

* Create request_id directive #1590

* Address Comments

* Fix TestListenerAddrEqual

* requestid: Add some tests

* Address Comments by tobya

* Address Comments

* introduced own ChallengeProvider type, based on acme.ChallengeProvider to avoid vendoring/version mismatches in Caddy plugins; see Caddy issue #1697

* fixed up comments for ChallengeProvider

* moved ChallengeProvider to caddytls/tls.go

Update Initscripts

"$(which caddy)" is not work at startup. 
After this change, I can run "insserv -d caddy" to start caddy automatically on boot.

* Update plugins.go

* Add extraInfo to eventHook

* Add extraInfo to eventHook

* Update run.go

* Update run.go

* Update run.go

Related to #1660 and #1667

* Browse: Show symbolic links and targets type properly
 * gofmt
Signed-off-by: Jonas Östanbäck <jonas.ostanback@gmail.com>

* Move symbolic link check in to isSymlinkTargetDir
Signed-off-by: Jonas Östanbäck <jonas.ostanback@gmail.com>

* Revert template change and show sym link folders as normal folders

* browse: Updated icons including symlink indicators

* Add grpc plugin directive

* Update plugin.go

Removed whitespace line

* Update plugin.go

Vendor all dependencies

The vendor/ folder was created with the help of @FiloSottile's gvt and
vendorcheck.

Any dependencies of Caddy plugins outside this repo are not vendored.

We do not remove any unused, vendored packages because vendorcheck -u
only checks using the current build configuration; i.e. packages that
may be imported by files toggled by build tags of other systems.

CI tests have been updated to ignore the vendor/ folder. When Go 1.9 is
released, a few of the go commands should be revised to again use ./...
as it will ignore the vendor folder by default.

* de-duplicates code for 'not' ops and replicates 'not' op for ends_with

* fixes incorrect test expectations

* Add not_starts_with condition.

This adds the opposite of the starts_with condition, to check if a
given string does not start with another string.

* Correct white space problems

* Add uri policy test cases
 * Add function definition
 * Add uri hashing policy
 * Refactor and extract hostByHashing and use in IP and URI policy
 * Rename to URIHash
Signed-off-by: Jonas Östanbäck <jonas.ostanback@gmail.com>

Fixes #1674

* Correct proxy policy documentation
Signed-off-by: Jonas Östanbäck <jonas.ostanback@gmail.com>

* Change first's select() wording
Signed-off-by: Jonas Östanbäck <jonas.ostanback@gmail.com>

Signed-off-by: Jonas Östanbäck <jonas.ostanback@gmail.com>

* Add check for maximum number of arguments to log directive
 * Add failing test case
Signed-off-by: Jonas Östanbäck <jonas.ostanback@gmail.com>

* Change else ifs into switch
Signed-off-by: Jonas Östanbäck <jonas.ostanback@gmail.com>

* Refactor
Signed-off-by: Jonas Östanbäck <jonas.ostanback@gmail.com>

* Typo
Signed-off-by: Jonas Östanbäck <jonas.ostanback@gmail.com>

* proxy: added 'health_check_port' to upstream

* proxy: `net.JoinHostPort` instead of `fmt.Printf` for upstream checks

* proxy: changing health_check_port type (int->string)

adding tests for invalid port config