[FR] linker script database

[ildar]

in case user didn't provide linker a scripts, c-nRF can do smarter then now.
Based on this input:

1. chip;
2. SoftDevice;
3. is this app or bootloader.

it can provide suitable linker script or generate it on the fly.

[Cierpliwy]

Can you suggest a change by sending PR? I'm not sure if it's that simple as there are a lot of other options to consider eg. custom sections, custom SoftDevice configurations, etc. which affect linker script.