BUG: CSharp's AssembleVersion must be of the format N.N.N.N

The specification for this field is major.minor[.build[.revision]]
where all components are integers.

Change-Id: I2474551144d39ce37853536ed24a22ffcfea72ce
BUG: RC part of tag not extracted correctly

The number post fix from a pre-release tag should be optional. And the
correct, cmake match is used.
x
SimpleITK's RC version component is not extracted from the tag.

Change-Id: Ic48beb5084b3974d5b1051dfe2218d6a8c2aabf4
The _GIT_VERSION variables for patch should come from tag

These variable should not get defined with their implicit values. To
make the correct comparison with cmake VERSION_EQUAL, the defaults are
added when the version is compiled.

Change-Id: Ife932d293fabc995c268284edf709f540e7434f3
SourceVersionVars was defining empty variable.

The documentation for SourceVersion, states that these variables will
be undefined if they are undefined in the tag.

Change-Id: I8b84c254d8f769f6cf50f03760f53d77a3400536
Updating documentation in .i files from SimpleITK doxygen.

Change-Id: I8edbedd1d4293190686f8de072c2d12dcc42d179
Merge topic 'SIMPLEITK-327_AddGitBasedVersionInformation'

6cff964 SourceVersionVars was defining empty variable.
e3febc2 The _GIT_VERSION variables for patch should come from tag
b4fd739 BUG: RC part of tag not extracted correctly
a00b9a4 BUG: CSharp's AssembleVersion must be of the format N.N.N.N
Merge topic 'UpdateSwigDocs'

7b76618 Updating documentation in .i files from SimpleITK doxygen.