Shinken WebUI 2.6.0

This is a huge version. Could be major except it doesn't break anything important so I choose to keep it 2.x.
You can wait for 2.6.1 to see if some bugs pops up. But upgrade is really recommended.
IMPORTANT: If you are using mod-ui-pnp to display PNP4Nagios Graphs, please upgrade it to version 1.1 with cd /usr/shinken/modules; cp ui-pnp.cfg ui-pnp.cfg.bak && shinken update ui-pnp && mv ui-pnp.cfg.bak ui-pnp-cfg.

Features:

• New perfdata pie charts
• Perfdata table in host/service informations (using pie charts)
• Ctrl+Click and Maj+Click to select multiple elements in problems view
• User avatars : Generate and display user avatars if Gravatar is disabled or doesn't respond

Enhancements:

• Flat design (in fact this is a really little change)
• New colors for header menu and new Shinken logo
• New arrangement of problems view (better responsive)
• Rewrite problems widget
• Display all the graphs in problems view (Fixes #449)
• Loads graphs with ajax in problems view
• Use Bootstrap Tooltips instead of browser native management of HTML title
• Rewrite element comments and downtimes tabs
• Rewrite element history tab
• Cleanup overall states in header menu
• Cleanup element informations tab (Work in progress)
• Cleanup contacts view
• Cleanup commands and system views
• Round synthesis pct to one number instead of two
• More subtil stars display on business impacts
• Move JS includes at the end of HTML
• Lot of JS cleanup
• Added Cache-Control on graphs

Bugs:

• #583 Fix : disable refresh if refresh_period = 0 (Thank you @guillaume-u)
• Debug shinken-refresh.js
• #570 Fix save dashboard modification (currently view) (Thank you @bmalynovytch)
• Header menu on mobile
• Added webui version number on assets to avoid bugs after update due to browser cache

Removed features:

• Remove Perfometers (replaced by pie charts)
• Remove Depgraphs (completely buggy, no one was using them)

Again, if you are using mod-ui-pnp to display PNP4Nagios Graphs, please upgrade it to 1.1.