[nem-en] Assembly Version from SVN

[vc]

> It's probably because different dependencies in this context. To build
> new MBuild task you need a freshly built compiler...

Update boot, please.

> Thanks for the reference, I will use it. Though this approach has its
> own disadvantages - if svn changes its (internal!) format for storing
> revision number we will need to adapt (and actually check for all
> possible formats)

SVN is open source. If format will be changed we change our code too.

And code from reference is from work project. If SVN will be changed it also
will be updated.

> Also, I guess that attribute should be assemblyVersionFromSVNorDate
> and fallback to date if svn is impossible to get. Otherwise we would
> break builds for sources without svn metadata.

+1
Better use not date, but something incremental counter.