Expose module library installation location variable

See merge request e3/e3-require!3

Required to support installation of pre-compiled e3 module library
for OPC/UA module.

Simplification of DECOUPLE_FLAGS. The underlying mechanism of determining include paths, however, should be reviewed.

Fixed double negative, and removed old uninstall stage that deleted symbolic links that are no longer used.

Force E3_MODULE_NAME to conform to a proper form before build occurs. This will force e.g. ADCore to have E3_MODULE_NAME adcore. This is in keeping consistent with the conda system used at Utgaard.

Updating to 7.0.4 and require 3.2.0

See merge request e3/e3-require!1

Add dbdcat rules to E3 require

Added RULES_DBDCAT file extracted from RULES.Db in epics base. This is so that you can use DBDCAT within E3