blt acsf:init should be able to increase its memory usage

[nikgregory]

It we add the following to the acsf:init task
<echo>Increasing memory allocation to 2G</echo> <php expression="ini_set('memory_limit', '2G');"/>
or even better use a property which we default to some reasonable value
<echo>Increasing memory allocation to ${php.mem_limit}</echo> <php expression="ini_set('memory_limit', '${php.mem_limit}');"/>
users will not need to modify their php.ini for acsf:init to work.

This is especially useful in a pipeline build where there is no access to the php.ini

[nikgregory]

PR: #780

[grasmash]

Closed #780