Chameleon 1.7

Changes:

• (#49) Allows skins that build on top of Chameleon to set a specific layout
  file without the need to manipulate the global config variables.
  (Robert Vogel (HalloWelt)
• (#60) Add PageToolsAdaptable, an adaptable NavbarHorizontal/PageTools
  component (Tobias Oetterer)

Fixes:

• Create a stacking context on the main content to avoid elements with z-index
  messing up the nav elements (e.g. being shown in front of a sticky navbar
  instead of going behind it)
• (#65) Fix z-index for Echo notifications
• Remove usage of functions deprecated in MediaWiki 1.31