Handle BOMs in PB Sources.

[tajmone]

LemonPB needs to be tweak in order to handle BOMs in PB sources:

• Skip BOM when reading lempar.pb (but check that the BOM is actually there).
  • Add BOM back to lempar.pb.
  • Remove lempar.pb exception rule in .editorconfig.
• Add BOM to generated .pbi file.

Currently the BOM from lempar.pb is being injected in the middle of the generated .pbi file.