SVGHMI: Changes /CURRENT_PAGE_* behaviour to prevent problem whith multiclient : all clients were switching page when one was jumping.
- now PLC have to prefix page name with "!" to order page switch.
- HMI do not prefix with "!" when jumping, this avoiding looping incidently
- In case of multiple client:
CURRENT_PAGE reflects current page of last client hwo did jump
Setting CURRENT_PAGE with "!" affects all clients simultaneously

          <xsd:attribute name="Compiler" type="xsd:string" use="optional" default="gcc"/>
          <xsd:attribute name="CFLAGS" type="xsd:string" use="optional" default=""/>
          <xsd:attribute name="Linker" type="xsd:string" use="optional" default="gcc"/>
          <xsd:attribute name="LDFLAGS" type="xsd:string" use="optional" default=""/>