ZPM to support %SYS module install

[zrml]

Hi,

Issue:
Many applications need some initial % data pointers (global nodes) and initial routine(s) to check the environment or to start a background job, etc.
InterSystems IRIS offers the %SYS database with its %ZSTART, ZSTU and ZMIRROR.

Enhancement Request:
ZPM should allow a user to define %SYS installation modules so that if I needed to set a couple of application settings in a ^Global and run some initial code as the system comes up (ZSTU, %ZSTART, ZMIRROR), I could wrap those things in a ZPM module for %SYS.

Some links that may be useful:
ZSTU
%ZSTART and %ZSTOP
ZMIRROR

[isc-tleavitt]

This ends up becoming a release blocker because there are a lot of community packages that should be described in this way (the main set of differences between the master and v1 branches)

[isc-tleavitt]

The v0.9.0 implication here ends up being covered better by #470 - pushing the actual SystemRequirements aspect of this to v1.

[isc-dchui]

The spec is that you should be able to specify in SystemRequirements that this module should be installed in %SYS. If the current namespace isn't %SYS, it should fail.

Side note: might be nice to specify which database but that's way trickier.