This validator class will test an IP against a provide network notation. The
network notation can be a network range, or network address with CIDR or 32-bit
decimal subnet mask notation. Note that the main validation method always uses
the CIDR notation, i.e a bitmask will be converted into a CIDR.


Examples for network notations
------------------------------
Network Range: 
**************
128.0.0.12-128.0.0.19
true for all IP addresses inclusively in this range (i.e. from .12 to .19)

CIDR notation:
**************
128.0.0.8/30
block with 4 hosts
true for IP addresses from .8-.11 (i.e. .8, .9, .10, .11)

Subnet mask notation:
*********************
128.0.0.8/255.255.255.252
same as CIDR notation

Special Notes:
--------------
1) The network notation is validated, i.e. you have to pass a valid network and
CIDR or subnet mask combination. For the network range the two values must be 
valid IP addresses.

2) A CIDR notation of /32, subnet mask /255.255.255.255 or a range with two 
equal addresses will match for one host, i.e. the result is true if the network 
address or the range addresses are identical to the IP address

3) The network notation or a range has to be set prior to calling isValid() as
is custom with all Zend validators. The notation can be set when instantiating
the object as an array and 'network' as the index. The setter method is
setNetworkNotation($notation) and expects a string as the argument.