Update the setCartPrices function to the latest code from VM3; change getShippingCosts to getValue, because not all rules are really shipping costs any more

Propapate the plugin to the rules
Make many functions protected in the rules
Cache the rules and the match for each method
Evaluate each rule only once
Prepare for scpoding functions and plugin API

Try to clearly separate the calculation between rule and plugin; Add plugin mechanism; implement modifiers

VirtueMartModelState::getStates and VirtueMartModelCountry::getCountries changes the internal cache ->_data, but does NOT modify ->_id...
The proper fix would be in VM's model classes to set the id to -1.

However, as a workaround we can call setId twice to ensure the cache is always invalidated and getData returns the proper object

Version 4.0.1: Handle = and html in the basic plugin's rule names; hide the quotes around rule names in the basic plugin; fix typo in the operator regexp

Version 4.0: Fix globals warning; Add Values_Debug variable; Add contains_any/contains_all functions

V3.96: Apply bugfixes in the setCartPrices function (from the VM repo), which I had to copy from vmpsplugin.php

-) Implement custom definitions (Variable or Definition as keyword) of the form:
    Variable|Definition=VARNAME; [Value=]SOMECOMPLEXVALUE
-) Such defined variables can be used in all further rules.
-) Add "Condition=" keyword to indicate that a certain value is a condition (e.g. a variable defined as implemented here).
   This is needed to distinguish single-variable (or function-call) conditions from shipping costs, where the "Shipping=" was left out.
   Previously, only terms that contained a comparison operator were detected to be conditions. This excluded conditions like
   "issubset(...)" or "MyZIPConditions" (i.e. functions returning boolean values and boolean values stored in variables).
-) The rule-matching code was moved to its own function, so the logic to distinguish variable definitions and (later on) modifiers
   is in only one place.

Special care is taken (using a global array of messages...) to ensure that the message is not printed twice...

Internally, operators are converted to UPPER case, while function names are converted to lower case.