[webui] Rename Home to Watchlist

Description of watchlist is also misleading

The thing shows only the watchlist nothing else, so there are no
involved projects, plus you can watch something even if you are not
involved.

Make the link empty for watchlist

Actually having no js is not working for obs at all so no need to
have working link here.
This actually solves the issue that javascript did watchlist, but
the nojs is pointing to the home page.
[api] check the verifymd5 instead of the srcmd5 against jobhistory

Also check the now fast lastfailures route for the md5sum first - saving considerable
time in repo checker
[webui] adapt the test suite to Benjamin's latest fixes

It actually verified the broken state before ;(
[api] fix the test suite for /status/bsrequest
[api] introduce clockwork to replace cron dependency

clockwork can run jobs more often than one minute, already runs
as same user and has the ruby stack already loaded, so it takes
way less resources all in all
[activexml] in case of error, return Xmlhash not hash
[backend] fix cert generation that was broken by some earlier commit

It used the old private key to generate the cert, instead of the newly
generated one. Before that commit, cert generation was done as a
second step.
[api] delayed job has no user set, so fix crash there
[dist] travis recommends retrying

http://about.travis-ci.org/blog/2013-05-20-network-timeouts-build-retries/
[api] store the last number from lastevents in the database

It is pretty much overkill to have a table for a single value,
but it might get useful in the future and the alternative is writing
a file and it feels so unrailsy
[api] remove obsolete wrapper script
[api] scan linkinfos from backend and store them (as copy) in DB
[api] need to check given md5sum against srcmd5 and verifymd5

to be on the safe side, we check for both
[webui] remove file no longer needed
[api] fix the latest migration to the actual code

I screwed that up and test suite don't test migrations ;(
[api] fix performance problem when rendering json

as it turned out rails is forcing a specific (slow) json render, so
it doesn't matter how fast the json gem is if it's not used. So
overwriting the render used for render: json to generate json directly
instead of recursive to_json

Before project_infos/openSUSE:Factory: 1115ms - after 765ms, so it saves
on that project (with quite some packages) 350ms, which is not bad for
3 lines

Unfortunately JSON.generate can't be used within rails app due to
https://github.com/intridea/multi_json/issues/86 nonsense, so switch
back to yajl
[api] further speed improvements in webui#project_infos:

In Project#expand_all_packages don't bother loading all packages as
ruby objects if all we want to know is package name and project name

reduces runtime from ~590ms to ~370ms (the runtime varies a lot due
to backend parts involved, but I ran before and after each 4 times)

Additionally /source/<prj> also gets a gain

comparing /source/openSUSE:Factory and /source/openSUSE:Factory:Staging
with and without expand:

before
 O:F 727ms  O:F?expand=1 350ms
 O:F:S 9ms  O:F:S?expand=1 8722ms

after
 O:F 87ms OF?expand=1 111ms
 O:F:S 11ms O:F:S?expand=1 79ms

So factor 110 :)

Point of data: /source/openSUSE:Factory from srcsrv takes 172ms here,
/source/openSUSE:Factory:Staging?expand=1 take 240ms
[backend] get rid of the "Premature padding of base64" warning
[api] Minor fix in the InvalidParameterError message
[api] The webui API of the frontend is now much more RESTFUL