Added transparency support for HTML5

Change-Id: Ib9d63b636eeb66e3846e34ec4a54208a4d6550f2
Reviewed-on: https://iffwww.iff.kfa-juelich.de/review/77
Reviewed-by: Josef Heinen <j.heinen@fz-juelich.de>
Improved drawing of arrows

- use fixed size for arrow heads
- don't apply normalization transformation in NDC mode

Change-Id: I8b526b18d5bf454817450f671a78333ef1014cee
Reviewed-on: https://iffwww.iff.kfa-juelich.de/review/78
Reviewed-by: Josef Heinen <j.heinen@fz-juelich.de>
Improved image output in gr_mathtex function

Change-Id: I83cb4e5e1fd29ee63aa3c1747235e45a06c045ff
Reviewed-on: https://iffwww.iff.kfa-juelich.de/review/79
Reviewed-by: Josef Heinen <j.heinen@fz-juelich.de>
pygr: PlotAxes: Fix unexpected reset of window.

_resetWindow has been set to True on default to calculate a window
on the first drawGR call. If a window has been specified before the
first drawGR call has overwritten the window. Therefore set _resetWindow
to False on default and check for window is None inReset. This ensures
that a window will be calculated if no window has been specified but
does not overwrite an existing one.

Change-Id: Ifdb5856956dd285091e65c6fc1fa5a7f078ef5ee
Reviewed-on: https://iffwww.iff.kfa-juelich.de/review/82
Reviewed-by: Christian Felder <c.felder@fz-juelich.de>
Reviewed-by: Josef Heinen <j.heinen@fz-juelich.de>
pygr: Text: remove unused code.

Change-Id: I8e288db86ce7584118b206f5d434961aca0a98bd
Reviewed-on: https://iffwww.iff.kfa-juelich.de/review/81
Reviewed-by: Christian Felder <c.felder@fz-juelich.de>
pygr: Plot: Fix variable referenced before assignment.

If no title or subtitle has been set some variables has not been
initialized.

Change-Id: I24a0afee32688a2e5aec4968d04c4ed1be9c0e60
Reviewed-on: https://iffwww.iff.kfa-juelich.de/review/83
Reviewed-by: Christian Felder <c.felder@fz-juelich.de>
Improved 'gr_mathtex' output (transparency, color)

Change-Id: I89ad88a862dadc3e2a4216434ecbf8e9fef36c1d
Reviewed-on: https://iffwww.iff.kfa-juelich.de/review/84
Reviewed-by: Josef Heinen <j.heinen@fz-juelich.de>