Support for Tonal Bitcoin units (ᵇTBC, ˢTBC, and TBC)

Only available on dropdowns when a Tonal-compatible font is installed
Merge branch 'tbc' into 0.10.x-ljrF
Merge branch '1stclassmsg' into 0.10.x-ljrF
Merge branch 'bugfix_qt_uri_amount_parser' into 0.10.x-ljrF
Merge branch 'mempool_req' into 0.10.x-ljrF
Merge branch 'jonls_user-tx-filters-head' into 0.10.x-ljrF
Append user agent with /ljr(F):20141204/