FindCurses: Include CheckLibraryExists before using it (#15220)

Include the module at the top unconditionally so that all code paths can
use it.
ExternalProject: Convert docs to a bracket comment

Use a bracket comment to hold the documentation instead of a block of
line comments.  This will make further updates easier.  Also fix the
logic that parses options out of the documentation to be aware of the
new layout.
ExternalProject: Use explicit markup and definition lists in docs

Convert ExternalProject module documentation to use explicit markup
blocks for each command.  Enumerate command options with definition
lists instead of a literal block.  This will allow more detail to be
added later.  Also fix the logic that parses options out of the
documentation to be aware of the new layout.
CTest: Add Javascript coverage parser

Add a coverage parser for the Blanket.js library using the JSON output of
the mocha.js test runner.

Add a test for the new parser.
Merge topic 'FindCurses-include-CheckLibraryExists'

f11f9579 FindCurses: Include CheckLibraryExists before using it (#15220)
Merge topic 'add_javascript_coverage_parser'

220e8134 CTest: Add Javascript coverage parser
Merge topic 'ExternalProject-format-docs'

d9c2c17b ExternalProject: Use explicit markup and definition lists in docs
98936ae3 ExternalProject: Convert docs to a bracket comment
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