RNA: Added missing *srna's to curve functions.

RNA: Curves and VFont

Implemented RNA wrappers for curves and VFont. Only issue I could
not yet solve is related to struct CharInfo curinfo; . This particular
line proved to be hard to wrap and I therefore marked it as a TODO
should someone want to fix this issue.

I also cleaned up makesrna.c a bit by unifying brush/meta parts
under one call just the way it is done in the case of other
wrappers.

RNA:

Implemented RNA wrapper for ModifierData.

Note that actual interface to access data of any specific modifier is
still missing. I also marked a couple of parts as TODO that should be
reviewed to decide whether or not to expose those specific parts
via RNA.

RNA: brush wrapping

Wrapped most of brush. Brush is still missing a link to texture and to
BrushClone. Also PAINT_TOOL_DRAW etc. flags found on DNA_brush_types.h
need to be associated to a brush somehow. Currently they are linked
to a brush via ImagePaintSettings.

Also changed identifiers in metaball wrapping to conform with the
standards.

RNA: Support for Metaballs and Metaelements. I did not figure out a way to test latter but hopefully it works as well.

Fix for bug [#13651] Convertor->Math->Divide broken
Changed the if statement to catch zero case properly.

Nodes to be created at the location in which the mouse cursor was initially
This commit changes the way new nodes are created. Previously nodes were created
at the last location of the mouse cursor before creating a new node. After this
commit the nodes are created at the initial location in which the cursor was
before the menu used to add the node was opened.

This makes it possible for the user to predict where the new node appears without
having to move it to desired location like before. There is no option for this as
this behaviour is clearly superior to previous.

Codewise it uses static variables. This is something to fix during 2.50 rewrite.

Thanks to paprmh for contribution!

Minor changes to node rename tool
Rename was changed to work on the last selected node. Also size of a couple of
character arrays was changed to avoid buffer overflows.

Custom name shows up now just fine in group header in case it is being edited
as it did not before.

Custom Names for Nodes
This commit makes it possible to add a custom name to a node. The feature can be
accessed either by using a menu or shortcut ctrl-r. It currently works only when
a single node is selected. Invoking the feature gives a popup menu in which a new
name can be entered. If the given name is not empty, it will be shown like
"(myCustomName) NodeName" in the node header.

This feature is particularly useful when documenting complex node setups.

I also fixed the size of blur node. It was too short before due to my previous
commit.

Thanks to David Millan Escriva for contribution!

Blur Node to support Relative (percent) values
This commit makes it possible to use relative values when using a Blur node. There
is a new toggle in the node that can be used to enable the feature.

Thanks to David Millan Escriva for contribution!