Implemented OneByteIdentityH/V encoding cmap (with test pdf)

[hynekcer]

Some type of CID fonts with "Identity" cmap is problematic and nothing is extracted. An example is http://stackoverflow.com/questions/43832499/pdfminer-empty-output

I fixed it. The simple test file is taken from question http://stackoverflow.com/questions/38119176/itextsharp-font-widths-definition-not-correctly-loaded

Maybe a better or more general solution would be to use the existing /ToUnicode map, but my solution is similar to /Identity-H that also ignores the unicode map and believe that it is an identity.