Used equivalent implementations to those in the glTextTT class for some text
handling functions.
Used device information when obtaining font metrics.
Added a safer scaling calculation in the Text item.
Added scaling factors to the glText implementation as used by glTextTT.
Post process documentation before it is installed.

Summary:
Added a rule to replace a placeholder with the version number in the
         documentation so that we automate inclusion of the version in the
         index page.

Test Plan: Build and inspect documentation.

Reviewers: #diana, lisbethb

Reviewed By: #diana, lisbethb

Differential Revision: https://phab.met.no/D103
Added styles for different flight levels of ash cloud.

Summary:
Added styles to use different colours for each flight level.
Removed the fill colours from the ash cloud area styles.

Test Plan: Jenkins

Reviewers: #diana

Differential Revision: https://phab.met.no/D115
Bugfix: edit fields with no time axis
Improved highlighting of polylines and symbols

Summary: This change improves the highlighting of polylines and symbols several ways.

Test Plan:
Check that the highlighting of polylines and symbols provides a better
visual feedback when hovering over selected as well as unselected items.

Reviewers: lisbethb

Reviewed By: lisbethb

Projects: #diana_new_drawing_tool

Differential Revision: https://phab.met.no/D118
Merge branch 'master' of https://github.com/metno/diana