Create common crate, anchor cpi bindings crate

[0xripleys]

1. common crate (token-lending-common): holds all state, math, instruction stuff.
2. anchor crate (token-lending-anchor): cpi bindings for the solend program. It's only partially tested. I started writing a wrapper program to test every instruction via anchor CPI, but i think there are higher priority items atm.

[codecov-commenter]

Codecov Report

Merging #98 (7f0946b) into 0xripleys_bump_solana_version (d97079f) will decrease coverage by 6.33%.
The diff coverage is 0.71%.

@@                        Coverage Diff                        @@
##           0xripleys_bump_solana_version      #98      +/-   ##
=================================================================
- Coverage                          81.91%   75.58%   -6.34%     
=================================================================
  Files                                 32       32              
  Lines                               7715     7249     -466     
=================================================================
- Hits                                6320     5479     -841     
- Misses                              1395     1770     +375     

Impacted Files	Coverage Δ
token-lending-common/src/instruction.rs	91.75% <ø> (ø)
token-lending-common/src/state/last_update.rs	78.57% <ø> (ø)
token-lending-common/src/state/lending_market.rs	97.05% <ø> (ø)
token-lending-common/src/state/obligation.rs	92.91% <ø> (ø)
token-lending/program/src/lib.rs	100.00% <ø> (ø)
token-lending/program/src/processor.rs	71.37% <ø> (ø)
token-lending-anchor/src/lib.rs	0.47% <0.47%> (ø)
token-lending-common/src/lib.rs	100.00% <100.00%> (ø)
token-lending-common/src/math/decimal.rs
token-lending-common/src/math/rate.rs
... and 2 more

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