improve detection of dependencies installation for mac build
use template generation for build scripts

reason: avoid code duplication.
how to use: go in build_farm directory and run make.
remove usage of git submodule in build scripts

caused too much trouble:
- there were files staged after the operation (which blocked later
  automatic pulls)
- sub-repos were not updated if upstream pushed commits
Merge pull request #71 from duthils/build-farm

Build farm
pass only the qt root directory
nsis include imageformats plugins
fix typo in the path to create
fix strftime formating paramter, %F is not portable on windows
make sure we have a minimize button on the maindialog
the close 'X' button, just minimize
the exit button ask confirmation
plugin to handle ico format
do not show minimize button, not need because X use tray
linux: make sure /dev/net/tun is read/write for user
windows: use AppData to save conf files
windows: update nsis installer
update README
debian package: install the .desktop file and the icon
do not set auto_connect to on by default
dpkg --purge will call postrm, which will remove all conf files
use PNG instead of SVG, it will likely cause less troubles
update label font
do not show status pix while connecting
make sure the session->netc is valid
set the MSS to 1450 to accomodate different network MTU
add a button to check for update
make sure movie object are deleted in the class destructor
make sure the session->netc is not NULL