Adds getFootprint to the Part class to access the footprint composite.
Add a search / replace for the rendered text used for the parts. The text can now be user defined.
Adds a trigger_error if the TCPDF define K_TCPDF_CALLS_IN_HTML is set to true to ensure nobody will open a security hole.

This flag enables the usage of an extended version with inlining function
calls to php (which will be evaled) directly (inside a html text write).
As long as we use only code from our class, this is no problem, but an
implementer of a plugin may not think of this risk and should be reminded
with this.
Adds a new helper class to work also with relative and absolute values from
one parameter to give the user more flexibility while positioning things.
Adds a more sophisticated method to describe the labelling using html text for
the parts labelling. This gives the user a higher degree of freedom while
customising its label.