upgrade issues script to latest Dispatch, etc.
remove instance of 'the the' in various places
when extension not found, offer to take user to extension downloads page

closes #328
relocate plot.PlotAction to api package
cut dependency of prim.plot on plot package
merge prim.plot into prim.etc

since it doesn't have a dependency on org.nlogo.plot anymore,
there's no further need to have a separate package
splitting compiler into compiler and parse

a package is born!  this will facilitate cutting the front end's
dependencies on the engine, since we don't want Tortoise depending
on our JVM back end code
move more front end code to parse package
split ParserInterface off from CompilerInterface
rename CompilerServices -> ParserServices
cleanup: avoid importing parse._
rename packages: compiler -> compile, generator -> generate
graffle oops
update models submodule
minor cleanup
Merge remote-tracking branch 'origin/5.0.x'

Conflicts:
	src/main/org/nlogo/agent/AgentSet.java
whoops, make file name match class name
Merge commit 'e61d14d9115d31efa3e8e07a6a6dbdc31c822a6f' into tortoise-old
Merge commit 'de53d696bbe6abde72ce34c04c1881ef5413ae7a' into tortoise-old
Merge remote-tracking branch 'origin/master' into tortoise-old