Remove build and test Maven profiles in nuxeo-distribution

Since NXBT-656 and NXBT-568, the Maven profiles used in nuxeo-distribution to isolate the tests are now useless.
Worse, they may result in missing artifacts: the test-jar artifacts must be built even if not running functional tests. With the current POM, they will be missing unless activating the "all-tests" profile:
Could not find artifact org.nuxeo.ecm.distribution:nuxeo-distribution-cap-webdriver-tests:jar:tests:5.9.6-SNAPSHOT

Since Maven profiles are easily error-prone, those ones should be removed.

Profile "all-distributions" is expected to be activated by default but Maven profiles default activation is dropped when explicitly calling another profile.

      <id>all-distributions</id>
      <activation>
        <activeByDefault>true</activeByDefault>
      </activation>

A lot of XML code is duplicated to make the profiles work.

If a user wants to build only part of the distribution, he should rather use "-pl" and "-am" Maven options.
For instance:
"mvn clean install -pl nuxeo-distribution-cap -am" instead of
"mvn clean install -Pnuxeo-cap"

Main changes:

• default build will be equivalent to current build with "-Pall-distributions,all-tests"
• default build will include running tests unless using -DskipTests (or -DskipITs)