Explicit vocabulary lists and paragraph indentation.

[tomdonaldson]

Based on this e-mail thread, I made the following changes:

• Updated the Appendix B title to say V1.5
• Removed space from xtype="circle" in section 4.7
• Explicitly listed current vocabularies for TIMESYS timescale and refposition
• Removed \parindent=0pt to make paragraph breaks more apparent
• Added reference to architecture figure in section 1.4 to encourage better placement of the figure

In removing \parindent=0pt I noticed that we went from 35 to 32 overfull hboxes. Though I'm not sure that's necessarily an improvement, I didn't notice any new display problems in the draft pdf. This look does seem consistent with a couple other docs I looked at (DataLink and TAP). Please have a look for yourself at the pdf artifact generated for this PR.

Regarding whether some attributes of COOSYS should be mandatory to be consistent with TIMESYS, I've added this comment to issue 23, but still think we should maintain backward compatibility until version 2.0.
Please comment that issue if clarification is needed. If you'd to add something to this version warning that certain attributes may become required, please suggest wording here on this PR.

[msdemlei]

I'm fine with all the changes.

For the headline of the appendix you could consider using version \ivoaDocversion rather than updating things by hand, though.

[tomdonaldson]

I've added new commits for the latest apps list comments and to replace several lingering mentions of 1.4 that should have been updated to 1.5.

[mbtaylor]

I'm not convinced that resetting the \parindent (rather than adding a \parskip as suggested by Francois) results in an aesthetic improvement to the PDF, but if the editor prefers it that way it's fine (I know that \parskip sometimes doesn't behave as expected). Otherwise all looks OK.