Extract servlet-tools from taskmaster repo

[jonathanaustin]

Servlet-tools is a standalone submodule in TaskMaster that would be better as its own repo.

[jonathanaustin]

Projects using servlet-tools will need to add the new java-servlet-tools dependency as it is no longer provided by taskmaster-core.

<!-- Servlet Tools -->
<dependency>
  <groupId>com.github.bordertech.taskmaster</groupId>
  <artifactId>java-servlet-tools</artifactId>
  <version>1.0.0</version>
</dependency>

Refer to the new java-servlet-tools repo for more details.