Hardcoded cell model options

The hardcoded cell models are listed in the schema (.xsd) file, which should be present in any folder containing an xml parameters file.

In ChasteParameters_2_0.xsd, onwards the hardcoded cell models are

<xs:enumeration value="DifrancescoNoble"/>
<xs:enumeration value="FaberRudy2000"/>
<xs:enumeration value="FaberRudy2000Optimised"/>
<xs:enumeration value="Fox2002BackwardEuler"/>
<xs:enumeration value="HodgkinHuxley"/>
<xs:enumeration value="LuoRudyI"/>
<xs:enumeration value="LuoRudyIBackwardEuler"/>
<xs:enumeration value="MahajanShiferaw"/>
<xs:enumeration value="Maleckar"/>
<xs:enumeration value="tenTusscher2006"/>

In ChasteParameters_3_1.xsd, onwards the hardcoded cell models are

<xs:enumeration value="DifrancescoNoble"/>
<xs:enumeration value="FaberRudy2000"/>
<xs:enumeration value="FaberRudy2000Optimised"/>
<xs:enumeration value="Fox2002"/>
<xs:enumeration value="Fox2002BackwardEuler"/>
<xs:enumeration value="HodgkinHuxley"/>
<xs:enumeration value="LuoRudyI"/>
<xs:enumeration value="LuoRudyIBackwardEuler"/>
<xs:enumeration value="MahajanShiferaw"/>
<xs:enumeration value="MahajanShiferawBackwardEuler"/>
<xs:enumeration value="Maleckar"/>
<xs:enumeration value="tenTusscher2006"/>
<xs:enumeration value="tenTusscher2006BackwardEuler"/>