P1900092 v3: General suggestions

Referring to https://dcc.ligo.org/LIGO-P1900092-v3, circulated on March 27...

• X-Pipeline should have a capital P.
• Add reference citations for BAYESTAR, LALInference, X-Pipeline, and PyGRB.
• Cases 2 and 5 use the terminology "unmodeled transient", while cases 5 and 6 use the terminology "Burst". (Yes, case 5 uses both.) It would be better to be consistent. If "Burst" is used, it should probably be "GW burst" to distinguish it from the gamma-ray burst also discussed.
• A suggestion: change "Burst (model-dependent)" to "Rotational model" or "Ad-hoc rotational model". (The SEARCH is for an unmodeled transient / burst, but the hypothetical SIGNAL is modeled in a particular way for purposes of calculating an exclusion distance.)
• In case 6, the paragraph explaining exclusion distances all runs together; make it more clear when it switches to talking about the burst case.
• Case 7: remove the word "a" from the title, so it just says "Retraction of GW binary merger candidate"
• Saying "The preferred skymap at this time is..." is unnecessary if only one skymap is available. Therefore, I suggest putting in a bit of code so that sentence is included ONLY if there are two or more skymaps available.