add getBlockTimestamp and getBlockHeight

[eyalorbs]

In many cases it is necessary to know the block timestamp and height and it would be very helpful to add those functions

[EsterEdelstein]

Suggestion to add 2 commands:

• get-last-block - returners the height of the last block that was committed to the virtual chain . type- (uint).

• get-block-timestamp- returns the time stamp of the last block that was committed to the virtual chain . (uint): block timestamp as seconds since unix epoch .

This 2 commands should work with the option of -env and with orbs-gamma-config.json file

[talkol]

I'm pretty sure he didn't mean for gamma-cli, but for the contract SDK itself - meaning add SDK methods to allow to get these values from within running contracts

Closed in 45ff006