Fix a few compile bugs and minor corrections to the mikroe-stm32f4 configuration source.  From Ken Pettit

Rename CONFIG_EXAMPLES_NXCONSOLE to CONFIG_EXAMPLES_NXTERM; rename CONFIG_NXWM_NXCONSOLE to CONFIG_NXWM_NXTERM

SAMA5D4-EK:  Add documentation/support for Rev E. board. Refresh NSH configuration.  Fix some build errors/warnings introduced with recent work with the knsh configuration

Add the network enabled NSH configuration for the STM32F4Discovery board with the STM32F4DIS-BB base board

Having a symbol table is an option.  There are no symbol tables with CONFIG_BUILD_KERNEL, for example.

ARMv7-A: Modify up_fullcontextrestore() for CONFIG_BUILD_KERNEL.  It changed CPSR while in kernel.  That will crash is the new CPSR is user mode while executing in kernel space.  Fixed by adding a SYS_context_restore system call.  There is an alternative, simpler modification to up_fullcontextrestore() that could have been done:  It might have been possible to use the SPSR instead of the CPRSR and then do an exception return from up_fullcontextrestore().  That would be more efficient, but I never tried it.

Misc fixes to repair some of the breakage to the SAMA5D4-EK elf configuration caused by changes for the knsh configuration

When a privileged thread exits, we have to use the kernel alloctor to free memory; when an unprivileged thread exits, we don't have to do anything... heap memory will be cleaned up when the address environment is torn down