Swap roles of master and legacy-support.

A while ago legacy-support became de-facto master branch. Moreover, due to experimental nature of changes in master, they would fit better in experimental. Additionally, a lot of changes in legacy-support was intended to increase stability of framework without any breaking changes or something.

That's why I decided to change branching approach to more classic, with master and experimental branches, and make logical breakpoint in versioning, continuing legacy-support releases from 1.7-pre moment for versioning consistency.

Artifex/pom.xml

@@ -13,7 +13,7 @@
     <packaging>jar</packaging>
 
     <artifactId>Artifex</artifactId>
-    <version>1.7-dev.4+legacy_support.13</version>
+    <version>1.7-pre</version>
 
     <name>Artifex</name>