various problems solved with Giovanni:
  * removed pyenv check: not really useful
  * exception handling simplified trying to solve some bugs.
  * added checks for unmet pip requirements using a basic versioning system.
a function call was missing to correctly mail the exception.
added --working_path argument to bin/startglobaleaks
restartclean.sh refactored and some code integrated into startglobaleaks (--restart_clean 1 to enable it)
added os.chdir() call on GLSetting.working_path
added possibility to define user queries (yes/no answer). this permits to define Horrors but in a safe way! :)

in reference to: https://github.com/globaleaks/GLBackend/commit/d2e91777c00f0f736a679af0aa72458092a462df#commitcomment-2910204
added --uid and --gid options and code integrated with twistd.
gid and uid of process must be setted before of directory creations.
bugfixing related to setuid/getuid/getpass
added check to avoid globaleaks to be runned by root user
pip requirements freezed (first attempt :P)
Merge branch 'master' into feature/thumbnails

Conflicts:
	bin/startglobaleaks
	globaleaks/utils.py
	requirements.txt
Merge branch 'feature/thumbnails' of github.com:globaleaks/GLBackend into feature/thumbnails

Conflicts:
	bin/startglobaleaks
preserved static files with new working_dir