Fix debian/copyright format for empty-short-license-in-dep5-copyright

Lintian reports empty-short-license-in-dep5-copyright warnings.
The License field in debian/copyright should not be empty by dep5 standard.
This commit adds the missing empty field.

Signed-off-by: Ying-Chun Liu (PaulLiu) <paulliu@debian.org>
Use system libjs-excanvas

In Debian, there's system-wide libjs-excanvas. This commit makes
tribler to use excanvas.js from system instead of local one.

Signed-off-by: Ying-Chun Liu (PaulLiu) <paulliu@debian.org>
Merge pull request #860 from grandpaul/fix-copyright-format

Fix debian/copyright format for empty-short-license-in-dep5-copyright
Revert libx11-6 back in debian/control Depends.
Merge pull request #861 from grandpaul/use-system-libjs-excanvas

Use system libjs-excanvas
Add 'Credit Mining' panel
Add header to credit mining panel
Set investment yield text
Also show speed on credit mining overview
Added some additional counters
Text changes
Add share_mode param to Session.start_download
Add get_share_mode/set_share_mode to LibtorrentDownloadImpl
Initial channel boosting code
Fix for SeederRatioPolicy
Added RandomPolicy
Start ChannelBooster in tribler.py + delete share_mode downloads from
previous run
Add more parameters to command line tool
Initial channel boosting GUI
Added RSS feed + tracker scraping + bug fixes