extracted methods download_binary_cache(), update_binary_cache(),
_pre_destroy()

Conflicts:
	slapos/cli/register.py

this retains comments and avoids issues with unicode, multiline values
(certificates) etc.etc.

both ipython and bpython are built and provided with slapos. bpython is the
default now, with colorful drop down menus. we can choose later.

also removed related tests

Conflicts:
	slapos/grid/SlapObject.py

Allow to query the web site without copy/pasting the user SSL certificates.
The query should be like:
curl -X POST -H "X-Access-Token: ACCESSTOKENVALUE" "https://slaposmaster.example.org/myspace/my_account/request-a-certificate/WebSection_requestNewCertificate"

Access token is destroyed after usage.
The token validity is one day.