Support unicode characters in WMS Plot titles

[Joern Ungermann]

Currently, the WMS server only supports ascii titles. For complex formatting latex syntax is employed, which isn't looking nicely on QT-Widgets. One could simply use unicode characters for stuff like $^2$. A prototype implementation showed that this is easily feasible, but one important character $^-$ isn't displayed by matplotlib. This should be investigated.

https://de.wikipedia.org/wiki/Unicodeblock_Hoch-_und_tiefgestellte_Zeichen U+207B (8315) is not displayed.

[Reimar Bauer]

Prototype for unicode support in layer titles

Removes the seemingly superfluous "str" calls before utf-8 conversion. Replace latex formatting codes with unicode symbols that seem to work in both front- and backend. Changed relevant layers to use unicode strings for saif strings.

Fix issue #278

→ <<cset 795de846bf90>>