anchor.diff:  
   === Node filtering
   In many cases it is desirable to control which nodes are included or excluded from a topology. For instance it is
  -useful to be able to generate customised topologies for specific customers which include only regions/sites etc 
  +useful to be able to generate customised topologies for specific customers which include only regions/buildings etc 
   relevant to their filtered node set. To this end it is possible to define a node filter 
   which chooses which nodes are included in a generated topology.
   
  
positive.code: |===
  | Operation  | Definition  | Example
  | OR | key1=value1,value2 alternatively key1=value1;key1=value2 | asset-region=north,south
  | AND | key1=val1;key2=val2 | asset-region=north;asset-site=23
  | NOT | key1=!val1 | asset-site=!23
  |===
  
  Thus the following configuration means include only nodes with region `north` or `south` but exclude all nodes with site `23`.
  ----
  filter=asset-region=north,south;asset-site=!23
  ----
  The filters are designed to treat all selected text key entries as comma separated values (csv). This allows OpenNMS node-categories which are
  many to many entries to be dealt with as a comma separated list of values; routers,servers,web etc. 
  Thus we can select based on multiple separate node categories. The following configuration means show routers and servers on all sites except site 23.
  ----
  filter=node-categories=routers,servers;asset-site=!23
  ----
  The filters treat all asset table entries as comma seperated variables (csv). This also means that, 
  for instance asset-displaycategory could also contain several values separated by commas. e.g. customer1,customer2,customer3 etc.
  
  NOTE: You should make sure asset addresses and other free format asset text fields do not contain commas if you want an exact match on the whole field
  
negative.code: Regular expressions are also allowed. Regular expressions start with the ~ character. 
  You can also negate a regular expression by preceding it with !~.
  
  The following example will match against regions 'Stuttgart' and 'Isengard' and any building name which ends in 4
  ----
  filter=asset-region=~.*gar(t|d);asset-building=~.*4
  ----
  
  === Configuration
  