[4.1] Official CDT Release v4.1.0

[ericpassmore]

Version bump to v4.1.0

Will include the following in release notes.

The BLS host functions provided in CDT v4.1.0 and later are only compatible in Spring v1.0.0 and above. 
Running contracts which include CDT v4.1.0 BLS hosts will not execute in previously released Leap software. 
CDT v4.1.0 may still be used to compile and run contracts across both Spring and Leap when the 
BLS host functions are not used. 

[heifner]

The BLS host functions provided in CDT v4.1.0 and later are only compatible in Spring v1.0.0 and above. 
Running contracts which include CDT v4.1.0 BLS hosts will not execute in previously released Leap software. 
CDT v4.1.0 may still be used to compile and run contracts across both Spring and Leap when the 
BLS host functions are not used. 

Also the setfinalizer host function. Maybe should say something more generic:

The new host functions provided in CDT v4.1.0 and later are only compatible in Spring v1.0.0 and above. Running 
contracts which include new CDT v4.1.0 host functions will not execute in previously released Leap software. CDT 
v4.1.0 may still be used to compile and run contracts across both Spring and Leap when only pre-Spring host 
functions are used.