Removed unused methods and using directives

squash! Removed unused methods
FindCommitHashByChangesetId use compiled regex
Update() fixed for case when file cannot be checkout from TFS
GetRootChangesetForBranch catch VersionControlException
VersionControlException exception handling improved
Init branch crash fixed if branch already exist (big problem with `branch --init --all`)
Some changes by comments
Ask Tfs server tfs branches only once
Retry on timeout
GetChangesets()  asks changesets by parts
ParseEntries()  called only when really needed
Garbage collection added to `clone` and `branch --all` commands
`fetch all` output improved
ReadIdentity crash fixed
HasWorkItems crash fixed