src/lib/dhcpsrv/dhcpsrv_messages.mes

    Merged in branch 'trac3601'

Minor log message and comment wording

    Merged in #4095.

doc/guide/admin.xml
src/lib/dhcpsrv/dhcpsrv_messages.mes
src/lib/dhcpsrv/lease_file_loader.h
    minor clean up, typos

src/lib/dhcpsrv/tests/csv_lease_file4_unittest.cc
src/lib/dhcpsrv/tests/csv_lease_file6_unittest.cc
    removed unnecessary use of scoped_ptr

src/lib/util/csv_file.cc
    CSVRow::trim() - replaced use of std::vector<>::erase with resise

src/lib/util/versioned_csv_file.h
src/lib/util/versioned_csv_file.cc
    VersionedCSVFile::next() - reorganized to use input_schema_state_
    VersionedCSVFile::columnCountError() - new convenience method
    minor cleanups

Merged in change made to GitHub for ticket trac4111.

src/lib/dhcpsrv/client_class_def.cc
src/lib/dhcpsrv/client_class_def.h
src/lib/dhcpsrv/tests/client_class_def_unittest.cc
    New files that define client class storage classes and tests

src/lib/dhcp/classify.h
    Amended commentary to reflect how these classes are now being used.

src/lib/dhcp/option.h
    Added typedefs:
        boost::shared_ptr<Option> OptionPtr;
        boost::shared_ptr<OptionCollection> OptionCollectionPtr;

src/lib/dhcpsrv/Makefile.am
    Added entries for new files

src/lib/dhcpsrv/tests/Makefile.am
    Added entries for new file

src/lib/eval/token.h b/src/lib/eval/token.h
    Added typedef:
        boost::shared_ptr<Expression> ExpressionPtr;

Several minor cleanup items based on review comments.  Implemented
support for downgrading files from newer schema versions:

doc/guide/admin.xml
    amended text on upgrading memfile to discuss downgrading

src/lib/dhcpsrv/dhcpsrv_messages.mes
src/lib/dhcpsrv/lease_file_loader.h
    revamped log messages to accomodate downgrading

src/lib/dhcpsrv/memfile_lease_mgr.cc
src/lib/dhcpsrv/memfile_lease_mgr.h
    added commentary to MemfileLeaseMgr ctor
    automatic conversion logic accomdates both upgrading and downgrading

src/lib/dhcpsrv/tests/csv_lease_file4_unittest.cc
src/lib/dhcpsrv/tests/csv_lease_file6_unittest.cc
    replaced tooManyHeaderColumns test with downGrade test

src/lib/util/csv_file.h
src/lib/util/csv_file.cc
    added CSVRow::trim()

src/lib/util/tests/csv_file_unittest.cc
    added CSVRow.trim test

src/lib/util/tests/versioned_csv_file_unittest.cc
    added VersionedCSVFileTest.currentSchemaTest test
    replaced tooManyHeaderColumns test with downGrading test
    revamped tests to check  getInputSchemaState() and needsConversion()

src/lib/util/versioned_csv_file.h
    Updated commentary to describe downgrade support

src/lib/util/versioned_csv_file.cc
    enum InputSchemaState
    input_schema_state_
    input_header_count_
    getInputHeaderCount()
    getInputSchemaState()
    needsConversion()

    next(CSVRow& row) - now supports downgrading rows
    validateHeder() -  now throws if called when no schema has been defined,
    and supports downgrading rows

1. Updated Kea guide to note that removing the hooks-libraries
   configuration element does not always have the expected effect.
2. Moved some documentation from the dhcp_parsers.cc file to the .h file.
3. Expanded checking of the contents of the hooks-libraries configuration
   element.