Manuscript strings

In addition to the characters defined for GreekStrings, this class should allow the following uses as documented from the HMT project:

Punctuation

• two vertical dot punctuation marker ⁚ (= \u205A)
• "double-dagger" punctuation marker ‡ (= \u2021)
• end-of-scholion marker (mapped to Unicode "two vertical asterisks", aka "fish tail") ⁑ (= \u2051)

"Floating" diacritical marks

• diareses on vowels with breathing and/or accent
• macra
• brevia
• "floating" grave accents