updated app-schema mapping file schema
documentation update for GEOT-4510 (app-schema plugin -- allows maxFeatures to work with normalised datasources)
fix spelling mistakes
Merge remote-tracking branch 'upstream/master' into app_schema_maxfeatures_sql
fix typo
Merge pull request #269 from GeoffWilliams/app_schema_maxfeatures_sql

Geoff Williams work: 
Documentation and schema update for GEOT-4510 -- app-schema plugin should provide option to pass max features count through to SQL