Raise maximal decimal precision from 28 to 29

[fredericDelaporte]

• Adjust default registrations of decimal and currency accross dialects for consistency.
• Cease applying the decimal limit to Oracle double.
• Fixes NHibernate 5 precision maximum on decimal reduced vs. NHibernate 4 #1606

Details:

• MySQL prior to version 5: it seems it was stored as string so with a huge precision, bumping 19 to 29.
• SQLite: it does not handle precision/scale, it stores decimal in the same binary format than double. (Thus the HasBrokenDecimal set to true for SQLite, since it does not have a true decimal handling.) What should be changed then?
• Oracle: double raised to 40 by the way, because it stores them as decimal but read them as .Net double, so it should not be limited to .Net decimal capabilities.
• SybaseAsa9: default was 18,5 instead of 19,5.
• SybaseAse15: default was 18,0 instead of 19,5. Set as 23,5 for avoiding a possible breaking change for those storing 10^18 numbers with the previous default.
• Also standardizes Currency registration.

[hazzik]

Approved on a condition that tests pass.

[hazzik]

Need to update DriverTest.