different improvements

Hello,
this request contains multiple independent changes, I hope this is OK for you.
a) added two new sample projects: WoklistSCU and WorklistSCP
* implement complete DICOM worklist functionality.
* uses some Cyrillic characters (no, I am no Russian, but this characters are so easy to identify and Google Translate helps) to show support of different encodings

b) fixed decoding in case different character sets are used and the message contains any sequence items
* this fixes issue rcd#35 
* I tested this with the DICOM file attached to issue rcd#35, so I think this can be closed now

c) allow to specify a default character encoding for network communication (DicomServiceOptions.DefaultEncoding)
* defines the character encoding (e.g. Cyrillic) for received messages, if no encoding is defined inside the message. 
* Of course this setting is optional and behavior is unchanged if you do not set this option 
* <b>Remark:</b> This is NOT according to DICOM standard, but it solves problems with crappy 8bit implementations which use the local character set, but do not send any (0008, 0005) inside the message. 

d) a MaximumPDULength can be set in DicomServiceOptions
* This defines the maximum PDU length used for the communication.
* Of course, still the the PDU length defined by the remote AE is used, if the remote AE proposes a shorter PDU length. Default is still 16KB (as hard-coded before)