PIC32MX795F512H UART1 interrupt problem
You enabled the UART module, but its receiver and transmitter blocks remained unpowered. You need to set:

U1STAbits.URXEN = 1; //enable receiver
U1STAbits.UTXEN = 1; //enable transmitter


Setting GPIO mode by \$\texttt{PORTSetPinsDigital}\$ is unnecessary because PIC32 automatically switches the pin setting whenever a peripheral starts to use it.