TtsSpan builders for each TtsSpan type. DO NOT MERGE

The reason for separate classes for each type, instead of a more flat
structure is to enable easy discovery of the available arguments that
can be set. For L we'll have about 12 types with 30 arguments and
almost all of the arguments are type specific. In future releases
we'll introduce more arguments. With editors that have code completion
one can construct a span without having to consult the documentation.

For now it only contains Text and Cardinal types.

Change-Id: I94531e600133d9f4f59a4170cceef1ee7a360ca7
(cherry picked from commit 90b095aabd8a5c43723821dda37354fd2beb38fb)