Add documentation explaing what is meant by "installing a reactor".

	@tomprince reported
Trac ID	trac#6624
Type	enhancement
Created	2013-07-14 06:01:24Z

• The "Choosing a Reactor" howto explains all the different available reactors, and has sample code for installing them, but doesn't explain what it means to install the reactor.

• The "Reactor Overview" howto talks about a chosen reactor but doesn't explain (or link to) how it is chosen. (#6623)

• The documentation for twisted.internet.reactor says that importing it installs the default reactor if one hasn't been installed, and in anycase returns the reactor. From this, one can deduce that installing a reactor causes it to appear as twisted.internet.reactor

• The documentation for twisted.internet.main.installReactor and twisted.internet.reactor talk about installing a reactor, but don't explain it.

trac-id__6624 6624
type__enhancement enhancement
reporter__tom_prince tom.prince
priority__normal normal
milestone__ 
branch__ 
branch_author__ 
status__new new
resolution__None None
component__core core
keywords__documentation documentation
time__1373781684000000 1373781684000000
changetime__1373781684000000 1373781684000000
version__None None
owner__ 

Start with the “Choosing a Reactor” and “Reactor Overview” howtos, then read the API documentation for twisted.internet.main.installReactor and twisted.internet.reactor. Explain what installing a reactor means and how it relates to choosing or importing one, with links from the relevant howtos. Done means a newcomer can understand the term and find the selection process.