make addons blender versions consistent

finished

Increased Armature name maxlen to actual limit of 63. Could have also changed io_anim_c3d, but it's a prefix string - not making sense to increase max prefix length to max name length.

* default start frame changed to 1, consistent with Blender's default for scene
* removed spaces around operator docstrings because they're not stripped by Blender's UI
* added AMC exporter, requires the armature to have been imported from ASF

from Paulo Dias (paxnubis)

- no need to use self.properties
- close the file (py3.3 reports resource leak)
- dont use camel case for property names
- use property definition formatting like other scripts in trunk.