Allow setting a custom pom for the maven install task

[Parker_Young]

Much like you can for the standard uploadArchives and mavenDeployer combo, a way to specify a custom pom for the maven install task would be nice.

[Peter_Niederwieser]

Should work the same as for ‘mavenDeployer’:

install {
    repositories {
        mavenInstaller {
            ...
        }
    }
}